Many people transition from the very basics of Windows Movie Maker to Sony Vegas Pro, and then become incredibly advanced editors and content creators using the latter. Vegas Pro is great because while it might seem complex at first, an enthusiastic editor can find out the most complicated functions and simplify it for a novice. I've used the different instalments for about 5 years and I've only just learnt how to do frame-by-frame animation with it, but it gets far easier with time and patience.
Like Thranax, I use Vegas for video game edits, be it reviews or let's plays. It's great for audio and visual editing as well as special effects. It's a good start for anyone looking to make videos for YouTube, and combined with other software like Adobe products, it'll allow you to produce jaw-dropping creations.